Means for producing mercury electrolytically from acid solutions



April 27, 1948. H. R. ALLEY ET AL 2,440,238

MEANS FOR PRODUCING MERCURY ELECTROLYTICALLY FROM ACID SOLUTIONS Filed Dec. 9, 1942 jiwen {OPS HaroZd fiu illey fie zjamg fili reee g M, MM 27% YMML Patented Apr. 27, 1948 MEANS FOR PRODUCING MERCURY ELEC- TROLYTI'OALLY FROM ACID SOLUTIONS" Harold R.

Alley, Northbrook,:amd.EBcnjamin F.

Freebcrg, Chicago, in].

ApplicationDccember 9, 1942, Serial No. 468,396

"2 Claims. 1

The invention relates to means for producin metallic mercury electrolytically from an acid electrolite and a general object of the invention is to provide a new and improved-method and means by which the electrolytic reduction of metallic mercury from an acid solution containing mercury salts may be efficiently carried to completion.

Another object of the invention is to provide a novel 'method of this character which includes the steps of collecting the metallic mercury produced byelectrolysis in a mercury pool as the cathode 'of the electrolytic cell and maintaining the size of such 'pool constant by withdrawing mercury therefrom as fast as it is produced electrolytically.

Another object of the invention is to provide a novel means for producing .metallic mercury electrolytically which'includes-an electrolytic cell having as its cathode a pool of mercury arranged to be maintained constant by the. continuous withdrawal therefrom of mercury in an amount equal to that produced electrolytically.

Other objects and advantages will become apparent in the following description and from the accompanying drawing in which the single figure shows an electrolytic cell according to the invention. I

While the invention is susceptible of various modifications and alternative constructions, we have shown in the drawings and will herein describe in detail, the preferred embodiment, but it is to be understood that we do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Heretofore the electrolytic recovery of mercury from an acid solution has been impractical because the action of the acid in the electrolite on the metallic mercury produced electrolytically reverses the electrolytic action by returning the metallic mercury to its original salts.

The present invention overcomes this difficulty by utilizing as the cathode of the electrolytic cell a mercury pool having a surface area maintained constant by the removal of mercury from the cell as fast as it is produced electrolytically. The invention may be used to recover mercury from acid solutions or from materials from which the Cit or the ele'ctrolite.

a of the container.

Referring to the drawing, the numeral 10 indicates the container of an electrolytic cell. This container is preferably-of glass, ceramic material or the 'likewh ich is inert to the action of mercury The container has a top opening and its bottom wall H slopes or tapers inwardly and'd'ownwardly' to communicate with an outlet defined by a neck or stem 12. A suitable distance above 'thebottom wall an anode I3 is suitably -suspenderil as in this instance by anode leads H extending through and suitably sealed. to the walls of the container. The anode preferably is a flat perforate member or plate of platinum .and is suspended to extend transversely One or more cathode leads l5 extend through and are suitably sealed to the wall of the containerin the lower portion thereof; illiSlOWBI'POIilOH being occupied when the apparatus ism-use by a pool 16 of metallic mercur-y which is inelectrical contact with the cathode lead and hence forms the cathode of the cell.

Means is provided for removing mercury from the cell as fast as it is produced electrolytically. In the present instance this means comprises a conduit I! connected with the bottom outlet and having a return or reverse bend I8 therein which determines the height of the surface level of the cathode pool in the container. The return bend has an upwardly opening vent l9 to prevent the formation of a siphon.

It will be evident that this arrangement will be effective automatically and continuously to remove from the container that mercury which is plated out on the surface of the cathode pool. The quantity of mercury removed will be almost precisely equal to the quantity of mercury electrolytically produced whereby the surface area of mercury in the cathode pool will be maintained constant.

The effective surface area of the cathode pool is determined as an approximate balance between two opposing factors. On the one hand, the surface area should be large to provide an efficient and effective cathode area. On the other hand, the surface area should be small to minimize the reaction between the metallic mercury and the free acid in the electrolite. For any given set of conditions, these opposing factors may be empirically balanced depending on the concentration of mercury in the electrolite, the acid concentration of the solution and the current density. It has been determined that when these factors are fairly balanced the electrolytic reaction can be carried to completion or to substantial completion.

In carrying out the process an acid electrolite derived, for example, from the leachings from mercury ores, from acid solutions of mercury salts or waste, or from mercury residues and the like, is placed in the container. The acid of these solutions will under most circumstances be nitric acid in view of the insolubility of most mercury salts of other acids. The most efiective surface area of the cathode pool having already been de termined for the particular type of solution to be electrolyzed, the cell is energized.

The electrolytic cell may be and preferably is anode consisting of a fi-at perforate member suspended transversely in said container and having leads extending through and sealed in the side wall of said container in the lower-portion thereof, a cathode in the lower portion of said container below said anode and comprised of a static pool of metallic mercury, a conduit connected at one end to said outlet and having a reverse bend located above said outlet for maintaining constant the level of said cathode pool within the container, and an air vent opening upwardly from the top of said reverse bend in said conduit,

said conduit affording a passage for the continu- 4 ous removal of mercury from said pool as mercury is electrolytically deposited thereon.

2. An electrolytic cell for producing metallic mercury from an acid electrolyte containing a mercury salt having, in combination, a container for acid electrolyte, the bottom wall of said container sloping inwardly and downwardly and having a central outlet, a liquid cooling jacket about said container, an anode suspended transversely in said container in the lower portion thereof, a cathode in the lower portion of said container below said anode and comprised of a static pool of metallic mercury, and a conduit connected at one end to said outlet and having a reverse bend located above said outlet for maintaining constant the level of said cathode pool Within the container, said conduit affording a passage for the continuous removal of mercury from said pool as mercury is electrolytically deposited thereon.

HAROLD R. ALLEY. BENJAMIN F. FREEBERG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Number Name Date 387,961 Ryan Aug. 14, 1888 679,050 Gerouard July 23, 1901 712,218 Truesdell Oct. 28, 1902 871,162 Chaplin Nov. 19, 1907 1,027,495 McNitt May 28, 1912 1,900,996 Palmaer Mar. 14, 1933 OTHER REFERENCES The Metal Industry of Oct. 27, 1933, pages 415-418, an article by Newberry et a]. on the Electrolytic Refining of Mercury.

Transactions Faraday Society, volume 5 (1909), pages -48 inclusive. 

